CA1061640A - Arming fuze for artillery shell - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A fuze for an artillery shell to be spun about an axis generally parallel to the direction it is fired in comprises a housing formed with a central axially extending sleeve and with a chamber surrounding the sleeve. The pin is axially slidable in the sleeve and is retained in position by at least one ball. A spring wound in the chamber around the sleeve normally holds the balls in position to lock the sleeve in place and maintain the fuze in an unarmed condi-tion. This spring comprises a steel inner section lying against the sleeve and normally pressing the balls together against the pin, an outer section having a high coefficient of friction and engageable with the inner surface of the spring-containing chamber, and an intermediate section on between the inner and outer sections and having substantially more turns than both of these sections.

Description

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SPECTFIC~TION
Cross-Reference_to Related Ap~lication This application is related to copending and commonly owned concurren~ly filed patent application Ser. ~o. 241,018. `;
:, ' ' s Field of the Invention ~. ..
This application relates to a fuze for an artillery projectile or th~ like. More particularly this invention concerns a detonator fuze for a projectile that is spun about an axis parallel to its direction of travel, as for instance a projectile fired from a rifled gun.
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` Back~round of the Invention A detonator fuze is known having a rotor which is . .
aligned centrifugally when the shell is spun at high speeds.
A contact or primer pin is engageable against this rotor axially by spring pressure when it has been released by a ;~
ball-type detent which is normally helt shut by a spring wound about an axis parallel to the direction of displacement.
When the shell is firedJthe rifling of the gun imparts con-~iderab~ spin to the shell so that the spring pulls away from the ball-type detent, allowing the pin to move into alignment with the centrifugally oriented rotor and arming the projectile~ Before the projectile is spun in this manner it is bore safe, that is even accidental dropping or shaking up of the projectile cannot explode it.

This bore safet~ of the detonator must exist non onl~
prior to firing the projectile but also for a br~ time after ,, :
it is fired,as ~he projectile must not explode as soon as it ., ~ .'', ~

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leaves the muzzle of the gun or even be able to explode imme-diately as it leaves the muzzle. To this end a r~latively long .:
spriny is wound around -the ball-~ype detent so that a certain peri~od of time is necessary in orcler for the entire length of spring to unwind and allow the pin to move into the armed posi- .
tion. Ag a result of this multiturn construction there is con- .
siderable friction force so that it is almost impossible to calculate just when the projectile will be armed after it is -.
fired. Furthermore the balls o* the detent are themselves urged ~.
centrifugally outwardly with considerable force, ancl frequently :~
press on and deform the inner turns of the spring. This defor- ~.
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mation again increases the arming time so that it is not rare in such arrangements that a projectile strikes a given target ~.
before it is armed.
It has been suggested to avoid this latter inconven- .
nience, cleformat.ion of the inner turns of the spring, by pro- ~!.
.. viding a relatively hard split sleeve or the like within the spring, so that a relatively soft spring, for instance made of ~ .
synthetic-resin material, may be employed. Such an arr~ngement increases the construction cost of the fuæe and adds to its . size ancd bulkiness. Since the fuze must be fitted within a .. :
r:i. given projectile which is intended to explocie and destroy it- ~
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se~f it is essential that the size of the fuze be reduced to a minimum in order to maximize the amount of powder that can be ~? put in the bursting explosive~

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It is an object of the present invention to provide .

an improved fuze for an artiller~ shell or the like. ~.

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~ Another object is the provision of such a fuze which : " ':
arms the projectile a predetermined fixed time after the pro-~-.,. _z _ .

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jectile i9 fired.

Yet another object is the provision of an improved fuze which is relatively compact and inexpensive to manufac-ture.

Summary of the_Invent on These objects are attained according to the presen-t invention in a fuze of the above-described ~eneral type where-in the spring wound in the fuze chamber around the sleeve in which the pin-lockiny ball or balls are radially displaceable comprises inner, outer, and inter~edia~e sections. The inner section lies against the sleeve and normally presses the ball against the pin i~nd is made of a very hard material not deform-able by the ball. The outer section has a sur-ace with a high coeficient of friction so as to ensure that it engages the in-side wall of the spring-containing chamber and unwinds it at a predetermined rate after firing of the shell. The intermediate `~
section is of substantially more turns than both the inner and outer sections and serves almost e~clusively to establish the time delay before the projectile i9 armed a~ter it is fired.
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~` According to other features of this invention the inner and outer sections are wound about the sleeve in the di~
rection o~ spin of the projectile imparted to this projectile by the rifling of the gun. The intermediate section is wound in ` the opposite direction. The inner and outer sections are made in accordance with this invention of spring steel and the ;~

intermediate section of softer material, such as a high-density -polyethyl`ene or a polyamide.
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; With the system according to thP present inventiOn the outer spring section ensures the bore safe~y and transport saEety oE the shell as it tightly holds the en-~ire spring pack-et together. At the same time the inner section is not damaged by the balls holding the operating pin in place so that the un-winding of this inner section can be counted on to take a pre-determined length of time. The intermediate section, however, is relatively long, at least twice as long as either of the other two sections, and o~ easily determinad characteristics so that its unwinding can be exactly calculated to take a prede-; texminea length of time. In this manner a relatively ine~pen- .
sive construction allows a fuze to be employed which renders the shell completely safe beEore ~iring and insures that it -~ ;~
will be armed a readilv ascertainable interval a-Eter Eiring.
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Brief Description of ~he Drawin~
The above and other features, objects and advantayes will become mora readily apparent from the following, reference ;
!. beiny made to the accompanying drawing in which:
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FIG. 1 is a section through a -Euze in accordance with this invention in the unarmed invention;
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FIG. 2 is a view similar to FIG. 1 showing the -Euze in the armed position; and ..
FIG~S. 3 and 4 are sections taken alony lines III
and IV - IV of FIGS. 1 and 2, respectively.

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, - ~4-S~ecific_Descr~tion The fuze according to the present invention as shown in F'IGS. 1-~ has a housing 1 in which a pin 3 is displaceable along an axis A within an internal sleeve 4.
A spring 2 urges the pin 3~ which is formed with a circum-ferential groove 3a, upwardly along the axis A. The sleeve 4 is formed with three radially extending holes 6 in each of which is normally received a ball 5 engageable within the groove 3a in order to lock the pin 3 axially in position.
A spring packet indicated generally at 7 holds the balls in the groove 3a normally to maintain the fuze in the unarmed position as shown in FIGS. 1 and 3.
The housing is formed with an annular generally cylindrical chamber 8 surrounding the sleeve 4 and having an inside surface 8a turned toward the sleeve 4. The spring pack 7 is received in this chamber 8 and comprises an inner section 7a resting against the balis 5, an intermediate section 7b 7 and an outer section 7c The inner and outer sections 7a and 7c have a relatively short overall length so that they have much fewer turns than the intermediate section 7b. Sections 7a and 7c are both made of spring steel and the section 7c is provided on all of its outside surfaces with a synthetic resin coating that increases its coefficient '-;,~ , of friction with the surface 8a and with the intermediate section 7b. This surface is also roughened in order to increase its coefficient of friction. Section 7b is made of synthetic-resin material~ a hard resin of the nylon or polyamide family being employed. The section 7a is~ as . ~. -mentioned above J made of spring steel and of sufficienthardness that the steel balls 5 cannot deform it. The sec-tions 7a and 7c are as shown in FIGS. 3 and 4 wound against the direction of spin D of the projectile carrying the fuze housing 1 and the section 7b is wound in this direction D.
The sleeve 4 is insulated from the housing 1 by elements 9 and 10. The housing is also provided with a rotor 11 carried on radially extending pins lla received in journals 12 in the housing 1. When spun at high speed about the axis A the rotor 11 tends to twist about its transverse axis A' from the position shown in FIG~ 1 to the position shown in FIG. 2. The pin 3~ however9 normally rests in a recess 16 formed in the rotor 11 so as to prevent the rotor 11 from moving into the position of FIG. 2 in which the contact pin 13a of a primer 13 is aligned along the axis A
with the pin 3. A foil 15 is provided over a window above the rotor 11 to allow the primer 13 to be connected to a conventional fuze or operated in any other manner and also to allow the detonator to be withdrawn from its bore 14 in .:`
the rotor 11.
The fuze operates as follows:
, Prior to firing, that is during transport~ loading, and when in position in the gun bore, the fuze is in the position shown in FIGS. 1 and 3 with the pin 3 seated in the ` recess 16. The balls S lock the pin 3 in this predetermined axial position and prevent the rotor 11 from rotating about its axis A~. Even if the projectile carrying this fuze is dropped or grossly mishandled the elements will remain in .

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;l this position as only high-speed spinning of the housing 1 about the axis A can unlock these elements relative to one . .
another.
- When the shell is fired it is spun about this axis A at a very high speed so that first the outer section 7c of the spring packet 7 will suddenly unwind and engage the surace 8a of the chamber 8 7 very quickly unwinding and lying against this surface 8a. This frees the spring 7b which now unwinds at a very readily determined rate, as it is wound in the direction of spin of the housing 1~ and it is in engage~ent with the surface of the section 7c which has a very high coefficient of friction. Once the section J,' 7b has fully unwound~ taking a relatively long time~ the inner section will also very quickly unwind~ as it is wound opposite to the direction D. This allows the balls 5 to move radially out of their bores 6 as indicated in FIG. 2~
The pin 3 is now free to move in the direction of axis A. Since the rotor 11 is being urged by centrifugal force to move into position of FIG. 2 it will depress this pin 3~ causing it to leave the recess 16, until the contact pin 13a is directly axially aligned with the pin 3 whereupon ; the spring 2 will push the pin 3 up against this pin 13a.
An electrical connection is now made between the pin 3 and the contact pin 13a so that the primer 13 is armed. ~iring of this p~imer 13 can be effected by an electrical current passed between the sleeve 4 and the primer 13 by an impact fuze or the like such as described in the above-cited com-monly filed patent application.

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Since the intermediate section 7b is relative]y long and is wound in the direction of rotation of the fuze, its unwinding time can be relatively easily ascertained and controlled within very strict limits. Thus the shell can be counted on to become armed at a predetermined instant after it leaves the muzzle of the gun. At the same time the relatively hard section 7a is not marred by the balls so that it also unwinds rapidly~ and the section ~;
7c having a high coefficient of friction also unwinds rapidly. Both of these sections 7a and 7c are wound against , the direction of rotation D of the fuze so that their un-winding time i5 nominal compared to the unwinding time of .
' the intermediate multiturn section 7b.
It is noted that in FIGS. 3 and 4 the spiral springs ; 7a-7c are shown with their individual turns spaced apart for `
clarity of view. In reality in both positions corresponding to FIGS. 3 and 4 the turns of each spring 7a, 7b and 7c lie , on one another and each such spring lies directly on the ' neighboring spring.
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Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fuze for an artillery shell to be spun about an axis generally parallel to the direction it is fired, said fuze comprising:
a housing formed with a central axially extending sleeve, an inner surface facing said sleeve, and a chamber between said sleeve and said inner surface;
a pin axially slidable in said sleeve;
at least one ball radially displaceable in said sleeve and radially engageable with said pin to arrest same; and spiral spring means in said chamber around said sleeve and including an inner spring element lying against said sleeve and normally pressing said ball against said pin, said inner element being of very hard material not deformable by said ball, an outer spring element engageable with said inner surface and having a surface with a high coeffici-ent of friction, and an intermediate spring element between said inner and outer sections having substantially more turns than both said inner and outer elements.

2. The fuze defined in claim 1 wherein said inner and outer elements are wound about said sleeve in the direction of spin of said projectile and said intermediate element is wound in the opposite direction.

3. The fuze defined in claim 2 wherein said outer element is coated with a synthetic-resin material having a high coefficiant of friction.

4. The fuze defined in claim 2 wherein said inner and outer elements are of steel.

5, The fuze defined in claim 2, further comprising a rotor pivotal in said housing about a transverse axis extending perpendicularly to the spin axis between a pair of pivotally offset positions and having a recess positioned to receive said pin in one of said positions and a contact member alignable with said pin in the other of said positions.

6. The fuze defined in claim 2 wherein said outer element has a roughened surface.

7. The fuze defined in claim 2 wherein said intermediate element has at least twice as many turns as either said inner or said outer element.